The invention relates to a carbon-containing hard coating as well as to a method for depositing a hard coating onto a substrate.
In a variety of important applications, e.g. in the field of cutting tools for milling, turning, or drilling, in the case of molds or mechanical components like bearings, dies, rolls, or for example in the wide range of engine-components, it is popular to coat hard coatings onto stressed surfaces in order to have superior wear resistance, oxidation behavior, and friction properties.
Hard coatings containing titanium nitride are widely spread in a great variety of applications, wherein by adding carbon and aluminum forming TixAlyNz and/or TixCyNz chemical compounds, the hardness of titanium nitride coatings may be increased due to enhanced chemical bonding. In addition, the aforementioned MeCN compounds may be embedded into an amorphous-carbon phase reducing the friction coefficient of the hard coating. Furthermore, it is well known that TiAlN has better oxidation resistance than TiN as a consequence of the formation of an aluminum passivation layer on the surface.
In particular in the field of high-speed-machining, high frictional forces arise, especially if coated parts are pressed against each other by great forces causing additionally high temperatures as well as enormous longitudinal and transversal mechanical stress in the coating. The problem is that known conventional hard coatings do not have at the same time a sufficient wear resistance and a low friction coefficient, especially at higher temperatures, so that strong abrasion damages are caused in the coating after only a short time of operation.